Polyester laminated building boards with improved surface characteristics

ABSTRACT

This disclosure relates to using polyester films on building boards to enable improved surface coatings. The polyester film is preferably applied to a glass mat via an adhesive to form a laminate. This laminate is then bonded to the exterior surface of a gypsum board. The polyester film is advantageous because it allows for exterior surface coatings to be applied. In one embodiment, an exterior acrylic coating is applied to the polyester film. Boards constructed in accordance with this disclosure allow for exterior finishings to be achieved without the need for excessive finishing materials or steps.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 14/153,260, filed Jan.13, 2014, which is incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to the use of polyester laminates in buildingboards. More particularly, the present disclosure relates to usingpolyester laminates to improve the surface characteristics of buildingboards.

BACKGROUND OF THE INVENTION

For over a century, wallboard has been used as an interior wallcovering. The most common type of wallboard is gypsum wallboard. Thebasic construction includes a core of cementitious gypsum that ispositioned between two opposing paper liners. One of the paper linersforms the exterior wall finishing. An example of a paper-covered gypsumboard is illustrated in U.S. Pat. No. 2,806,811 to Von Hazmburg. VonHazmburg discloses a board that primarily consists of a thick gypsumcore that is encased in a fibrous envelope consisting of both a manilasheet and a newsprint sheet. These sheet layers can be made from aconventional multi-cylinder paper making process.

It is also known to replace the paper facing sheets with opposing glassfiber mats. This construction is referred to as glass reinforced gypsumboards (or “GRG”). A GRG board is disclosed in U.S. Pat. No. 4,265,979to Baehr et. al. A further improvement was realized by slightlyembedding one or more of the glass fiber mats into the core slurry ofthe board during the manufacturing process. This results in a thin filmof slurry being formed on the outer surface of the board. Buildingboards with this construction are referred to as embedded glassreinforced gypsum (EGRG) boards. EGRG boards eliminate, or greatlyreduce, the presence of exposed fibers.

Yet, paper faced boards, GRG boards, and EGRG boards, all requireextensive finishing materials and labor intensive steps in order toachieve a desirable exterior wall finishing. According to the GypsumAssociation, wall finishings are measured on a scale ranging from theleast smooth (Level 0) to the most smooth (Level 5). A level 0, theexterior surface of the board is rough and or textured in appearance.Contortions and undulations are easily visible upon the board. At Level5, the exterior surface of the board has a very smooth appearance thatapproximates glass.

Paper faced gypsum board is not capable of yielding a Level 5 finishwithout the incorporation of special sealers and multiple skim coats ofa finishing compound. Sanding is also required as each level is builtup. Hence, achieving a Level 5 finish with paper faced boards is a laborintensive process that requires a variety of added materials.

Forming a Level 5 finish on GRG or EGRG boards can prove equallyproblematic albeit for different reasons. GRG and EGRG boards have acementitious surface and/or core that is filled with desiccant-likematerials. Thus, when finishing compounds are added to the surface ofthese boards, they are quickly absorbed. To be effective, large volumesof finishing compounds must be used. The absorption of the finishingcompounds can also cause voids, cracking, premature desaturation andresultant quick set. All of these precludes the formation of a Level 5finish on GRG or EGRG boards.

Various efforts have been made over the years to reduce the materials,labor, and time needed to adequately finish the exterior surface wallboards. For example, sprayable compounds have been developed to providewall boards with Level 4 or Level 5 finishes. Yet, these sprayablecompounds suffer from all of the aforementioned drawbacks. Paper facedboards do not saturate quickly enough. As a result, sprayable finishesrun when applied to paper faced boards. By contrast, glass reinforcedboards absorb liquids too quickly. As a result, unnecessarily largevolumes of spray must be used in order to achieve a desired finish.These problems can only be overcome by using skim coatings orspecialized primers, which only adds to the time and expense of thefinishing effort.

The composite building boards of the present disclosure are designed toovercome these drawbacks by utilizing a polyester film to achieve asmooth exterior finish with minimal finishing materials, time orexpense.

SUMMARY OF THE INVENTION

This disclosure permits smooth exterior finishes to be applied to wallboards with minimal finishing materials, time, and expense.

One advantage of the present disclosure is realized by utilizing apolyester laminate to produce a wall board having a smooth exteriorfinish.

Yet another advantage is attained by employing a polyester laminate asthe base for an exterior acrylic coating, which itself provides asatisfactory surface.

Still yet another advantage is achieved by adhering a polyester film toa fibrous mat via a hot melt adhesive, thereby producing a laminate thatcan facilitate the formation of smooth exterior surface.

Another advantage is reached by adhering an acrylic lined polyester filmto a fibrous mat via a hot melt adhesive, thereby producing a laminatethat provides a smooth exterior surface.

A further advantage is realized by using a perforated polyester film inthe creating of a building board with a desirable surface finishing.

The building boards of the present disclosure enable the formation ofLevel 5 finishes without the need for extra finishing materials andwhile minimizing time, labor, and expense.

Various embodiments of the invention may have none, some, or all ofthese advantages. Other technical advantages of the present inventionwill be readily apparent to one skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following descriptions, takenin conjunction with the accompanying drawings, in which:

FIG. 1 is a cross sectional view of a building board made in accordancewith the present disclosure.

FIG. 2 is a side elevational view of a production line for producingbuilding boards in accordance with the present disclosure.

FIG. 3 is detailed view of the production line taken from FIG. 2.

FIG. 4 is a side elevational view of an alternative production line forproducing building boards in accordance with the present disclosure.

FIG. 5 Is a detailed view of the production line taken from FIG. 4.

FIG. 6 is a sectional view taken from Line 6-6 of FIG. 3.

FIG. 7 is a sectional view taken from Line 7-7 of FIG. 5.

Similar reference characters refer to similar components throughout theseveral views of the drawings.

DETAILED DESCRIPTION

The present disclosure relates to the use of polyester films tofacilitate improved surface finishings for building boards. Thepolyester film is preferably applied to a glass mat via an adhesive toform a mat/film laminate. The laminate is subsequently bonded to thesurface of a gypsum board. The polyester film is advantageous because itallows for exterior surface coatings to be applied. In one embodiment,an exterior acrylic coating is applied to the polyester film. Boardsconstructed in accordance with this disclosure allow for exteriorfinishings to be achieved without the need for excessive finishingmaterials or steps.

With reference to FIG. 1, polyester film 22 forms one layer of to acomposite, multi-layered building panel 24. Panel 24 can be formed fromopposing paper sheets with an interior gypsum core 26. In anotherembodiment, opposing fibrous mats 28 are used in lieu of paper sheets.Fibrous mats 28 are formed from randomly aligned organic or inorganicfibers that are held together with a binder. As with conventional EGRGboards, mats 28 are porous to allow mat 28 to be slightly embedded inthe gypsum core 26 during assembly.

Core 26 is formed from a set, crystalline gypsum matrix that extendsfully between, and is bonded to, the interior surfaces of the upper andlower fiber mats 28. In one specific but non-limiting example, theportion of core 26 proximate upper and lower fiber mats 28 has a densitythat is greater than the density of the remainder of core 26. In otherwords, the inner most extent of core 26 is less dense than the upper andlower peripheries. This helps strengthen the face of the board withoutunduly increasing the overall board weight.

In the preferred embodiment, polyester film 22 is formed frompolyethylene terephthalate (PET). However, the use of other polyesterfilms is also within the scope of the present invention. It is alsowithin the scope of the present invention to employ polymer films suchas, but not limited to, polyethylene, polypropylene, polystyrene,polyurethane, polyvinyl acetate, or polyvinyl alcohol films. Theinterior surface of film 22 can be modified to improve its ability toadhere to lower layers and to promote the formation of a laminate. Forexample, the interior surface can be modified via corona or flametreatments.

An adhesive 32 is employed in adhering polyester film 22 to the exteriorsurface of the upper mat 28. The preferred adhesive is a hot meltpolymer adhesive. The adhesive may be heat activated. Other polymerbased resins can likewise be used. The adhesive composition may includeadditives for ultraviolet (UV) resistance, antimicrobial resistance, orother additives to promote adhesion. A nip or roller can be used toactivate adhesive 32 and thereby join film 22 to the exterior surface ofthe upper mat 28. This step can be carried out prior to, and separatefrom, the other steps needed to produce the final composite board 24.Alternatively, film 22 and mat 28 can be joined together at a pointalong the board forming station 44 (note FIG. 2). Upper mat 28 with theadhered polyester film 22 together form a laminate sheet 42. Adhesive 32forms an outer stratum on fibrous mat 28 that is smooth and that issubstantially free of the fibers that make up mat 28. As a result, film22 produces a smooth outer application surface that is level inappearance. Film 22, thereby, presents an excellent surface forsubsequent finishing materials, such as acrylics or similar materials.In practice, the exterior surface of film 22 may consist of minortopographical inconsistencies ranging from a minimum depth of 0.001inches to a maximum of about 0.01 inches. In one possible alternative,film 22 can have an adhesive applied to both of its outer surfaces suchthat film 22 can be bonded to multiple different layers.

A finish coating 34 is thereafter applied to the exposed surface of film22. In the preferred embodiment, finish coating 34 is an acrylic.Acrylic coating 34 is applied to the surface of the polyester film 22 togive board 24 a smooth exterior surface finish. Acrylic coating 34 alsobeneficial because it provides paint adhesion and a matte finish. In analternative embodiment, the acrylic coating 34 may be adhered to thefilm 22 and mat 28 prior to laminate being delivered to the boardforming line 44.

Perforations can be formed in film 22 and/or in mat 28 to avoidblistering during the subsequent drying of board 24. This can beaccomplished by perforating film 22 prior to it being adhered to mat 28.Alternatively, the mat 28 and film 22 can be perforated together afterformation of the laminate. In either case, the perforations allow forthe transmission of vapor, including but not limited to water vapor,during the subsequent drying of composite board 24. More specifically,as the board passes through one or more driers, water vapor is liberatedfrom the partially or fully hydrated gypsum. Without the perforations,the water vapor that is driven out of the core 26 may cause blisteringor deformation of the upper paper or fibrous mat.

FIG. 2 illustrates one possible manufacturing process for producingbuilding board in accordance with the present disclosure. Mat 28 isunwound from a supply roll (not shown) and brought into contact withfilm 22. Mat 28 and film 22 are brought together between a nip roll 38and a chill roll 36. A die supplies adhesive 32 to the nip as the mat 28and film 22 are brought together. Adhesive 32 bonds film 22 to anexterior surface of mat 28. Together mat 28 and film 22 form a laminate42 that is subsequently delivered to production line 44. Gypsum slurryis then supplied to the surface of the mat 28 that is opposite theadhered film 22. The gypsum slurry is delivered from a mixer 46. Thefilm/mat laminate 42 is preferably embedded into the deposited slurry.Vibrators can be included to ensure a sufficient degree of penetration.The degree of penetration can range from 0.5% to 101%. Namely, thedeposited slurry can penetrate between 0.5% to 101% of thickness of thelaminate 42. An additional supply of a fibrous mat 28 can be deliveredfrom supply roll 48 to form the opposite side of the building board.FIG. 3 is a more detailed view of the nip roll 38 and chill roll 36. Thecross section of FIG. 6 also shows the resulting laminate 42.Specifically, laminate 42 is formed from fibrous mat 28, adhesive 32 andfilm 22.

It is within the scope of the present disclosure to apply both adhesive32 and film 22 in liquefied form as a co-extrusion. Film 22 can beapplied to mat 28 prior to arriving at the production line 44.Alternatively, as depicted in FIG. 2, film 22 and mat 28 can be adheredas part of a single manufacturing process. Film 22 can similarly beadhered at a point downstream of the production line 44. For instance,film 22 can be applied pre or post dryer. Film 22 can be chemicallypre-conditioned to chemically bond with compounds, softening agents,acids, alkalizers, waxes, or combinations thereof, within adhesive 32.This chemical bonding improves the mechanical and/or chemical adhesionbetween the film and adhesive 32.

FIGS. 4 and 5 illustrate an alternative manufacturing process. Thisprocess is the same in most respects to the above reference process.However, following the formation of the mat 28 and film 22 laminate, anacrylic coating 34 is applied overtop of film 22. FIG. 7 is a crosssectional view of the resulting laminate, which consists of mat 28,adhesive 32, film 22, and acrylic coating 34.

Although this disclosure has been described in terms of certainembodiments and generally associated methods, alterations andpermutations of these embodiments and methods will be apparent to thoseskilled in the art. Accordingly, the above description of exampleembodiments does not define or constrain this disclosure. Other changes,substitutions, and alterations are also possible without departing fromthe spirit and scope of this disclosure.

What is claimed is:
 1. A composite, multi-layered building panelcomprising: opposed upper and lower fiber mats, the mats being porousand each mat having an interior and an exterior surface; a set gypsumcore extending between and bonded to the interior surfaces of the upperand lower fiber mats, the portion of the set gypsum core proximate theupper and lower fiber mats having a density that is greater than theremainder of the set gypsum core; a polyethylene terephthalate (PET)film having an interior and an exterior surface; a polymer adhesiveadhering the interior surface of the PET film to the exterior surface ofthe upper fiber mat, whereby the PET film is bonded to the upper fibermat; and an acrylic coating applied to the exterior surface of the PETfilm, the acrylic coating providing a surface finish to the composite,multi-layered building panel; wherein the polymer adhesive forms asmooth outer stratum on the upper and lower fiber mats, the outerstratum being substantially free of the fibers that make up the upperand lower fiber mats.
 2. The building panel of claim 1, wherein theexterior surface of the PET film includes topological inconsistenciesranging from a depth of about 0.001 inches to about 0.01 inches.
 3. Thebuilding panel of claim 1, wherein the surface finish is a level 4 orlevel 5 surface finish.
 4. A building panel comprising: a first mathaving an interior and an exterior surface; a set gypsum core bonded tothe interior surface of the first mat; a polyester film having aninterior and an exterior surface; and an adhesive adhering the interiorsurface of the polyester film to the exterior surface of the first mat,the adhesive including an outer stratum substantially free of thematerial that makes up the first mat, wherein the outer stratum issmooth.
 5. The building panel of claim 4, wherein the mat is formed fromrandomly aligned inorganic fibers.
 6. The building panel of claim 4,wherein the interior surface of the polyester film includes an adhesiveenhancing treated surface.
 7. The building panel of claim 4, wherein theinterior surface of the polyester film includes an adhesive enhancingcorona treated surface.
 8. The building panel of claim 4, wherein theinterior surface of the polyester film includes an adhesive enhancingflame treated surface.
 9. The building panel of claim 4, wherein theadhesive is a hot melt polymer adhesive.
 10. The building panel of claim4, further comprising an acrylic coating applied to the exterior surfaceof the polyester film, the acrylic coating providing a surface finish tothe building panel.
 11. The building panel of claim 4, wherein thepolyester film is a polyethylene terephthalate (PET) film.
 12. Thebuilding panel of claim 4, wherein the polyester film is perforated. 13.A building panel comprising: a laminate comprising a perforated polymerfilm bound to a sheet; a core of set gypsum; the laminate embeddedwithin the set gypsum core; a polymer coating over an exterior surfaceof the perforated polymer film, the polymer coating providing a surfacefinish to the building panel; and an adhesive adhering the perforatedpolymer film to the sheet, the adhesive including a smooth outer stratumbeing substantially free of the material that makes up the sheet. 14.The building panel of claim 13, wherein the sheet is perforated.
 15. Thebuilding panel of claim 13, wherein the adhesive comprises a pressuresensitive adhesive.
 16. The building panel of claim 13, wherein thesheet comprises a paper lining.
 17. The building panel of claim 13,wherein the sheet comprises a mat of fibers held together by a binder.18. The building panel of claim 13, wherein the laminate is embeddedwithin the set gypsum core between approximately 0.5% to 101% of theoverall thickness of the laminate.
 19. The building panel of claim 13,wherein the polymer film is polyethylene terephthalate and the polymercoating is acrylic.